How to calculate VAT — adding it, and taking it back out
Adding VAT is a multiplication. Taking it back out of a tax-inclusive price is not a subtraction — that is where most of the mistakes are, and where a cent goes missing from the invoice.
Which direction are you going?
Every VAT question is one of two. Either you have a price before tax and need the total, or you have a total that already includes tax and need to know how much of it is tax. They use different formulas, and using the wrong one is the single most common error.
| You have | You want | What to do |
|---|---|---|
| A net price, tax not yet added | The total to charge | Multiply by the rate and add it on |
| A tax-inclusive total | The net amount and the tax within it | Divide by 1 + the rate |
Adding VAT to a net price
tax = net × rate ÷ 100
total = net + tax
- Net amount
- SAR 1,000.00
- Tax — 1,000.00 × 15 ÷ 100
- SAR 150.00
- Total to charge
- SAR 1,150.00
This is the direction most service businesses quote in: the customer is told the fee, and the tax is shown as a separate line beneath it.
Taking VAT back out of a tax-inclusive price
This is the one people get wrong. If a total of SAR 1,150 includes 15% tax, the tax is not 15% of 1,150. It is 15% of the net amount hiding inside it, so you have to find the net first.
net = total ÷ (1 + rate ÷ 100)
tax = total − net
- Total (tax included)
- SAR 1,150.00
- Net — 1,150.00 ÷ 1.15
- SAR 1,000.00
- Tax — 1,150.00 − 1,000.00
- SAR 150.00
Taking 15% of 1,150 instead would give SAR 172.50 — over-stating the tax by SAR 22.50 on a single invoice.
Why the second formula is a subtraction, not a multiplication
Once you have the net figure you could work the tax out two ways: multiply the net by the rate, or subtract the net from the total. They do not always agree, and the difference is a cent.
- Net — 1,000.00 ÷ 1.15
- SAR 869.57
- Tax by subtraction — 1,000.00 − 869.57
- SAR 130.43
- Tax by multiplication — 869.57 × 15%
- SAR 130.44
- Net + tax, using the second method
- SAR 1,000.01
The multiplication route produces a total one cent above the figure the customer was quoted.
The VAT / Tax calculator takes the tax as the remainder for exactly this reason, so the net and the tax always add back to the total you typed. It is a small thing until you are reconciling a month of invoices against a bank statement.
Doing it in BuzPulse
Open the VAT / Tax calculator
It is at /apps/business-calculator/vat-tax and needs no account.
Choose the direction
Add tax to a net figure, or remove it from a tax-inclusive one. This is the choice that decides which formula runs.
Enter the amount and the rate
Any rate you like — 5, 15, 20 or a rate with decimals. Nothing is hard-coded to one country.
Read the net, the tax and the total
All three are shown together, each with the working printed beneath it, so the number can be checked rather than trusted.
Put it on the invoice
In the Invoice Generator, tax is set per line rather than once for the whole document — so a bill mixing a standard-rated service with a zero-rated item still totals correctly.
Rates, and where to check yours
The arithmetic above works at any rate. Which rate applies to what you sell is a separate question, it varies by country and by product, and it changes — so check it against your own tax authority rather than against any calculator.
In Saudi Arabia the standard VAT rate has been 15% since 1 July 2020, and the authority that sets and publishes it is ZATCA. Some supplies are zero-rated or exempt, which is not the same thing as each other and not the same as being untaxed.
Common mistakes
- Taking the rate off a tax-inclusive total. 15% of SAR 1,150 is SAR 172.50; the tax inside it is SAR 150.00.
- Adding VAT twice — once in a quoted price that was already gross, and again on the invoice.
- Rounding each line and then rounding the total again. Round once, at the point the number is shown.
- Applying one rate to a mixed invoice. Set the rate per line if the lines are taxed differently.
- Quoting "plus VAT" to a consumer. Business customers expect net prices; consumers generally expect to see the figure they will actually pay.
Frequently asked questions
- How do I remove 15% VAT from a price?
- Divide the total by 1.15. The result is the net amount, and the tax is whatever is left when you subtract that net amount from the total.
- Is the calculator locked to 15%?
- No. You type the rate, so it works at 5%, 20%, 7.5% or anything else. Nothing in it assumes a country.
- Does the invoice generator put a ZATCA QR code on the invoice?
- Yes, when the seller has a VAT registration number saved. The code carries the five fields the Saudi rules define — seller name, VAT number, timestamp, total including VAT, and the VAT amount. With no VAT number saved the invoice prints without a QR, which is correct rather than degraded.
- What is the difference between zero-rated and exempt?
- Both mean no tax is charged to the customer, but they are treated differently for reclaiming the tax you paid on your own purchases. Which category a supply falls into is a question for your tax authority, not for a calculator.
The tools behind this
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About the author
Naeem Ahmed builds and runs BuzPulse. These guides describe tools he has built, and they describe how those tools actually behave — including where they stop.
Corrections and questions: nsglobal6@gmail.com
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